MCQ
$\int_0^{2 / 3} \frac{d x}{4+9 x^2}=$
  • A
    $\frac{\pi}{12}$
  • $\frac{\pi}{24}$
  • C
    $\frac{\pi}{4}$
  • D
    $0$

Answer

Correct option: B.
$\frac{\pi}{24}$
(B)
$\int_0^{2 / 3} \frac{d x}{4+9 x^2}=\frac{1}{9} \int_0^{\frac{2}{3}} \frac{d x}{\left(\frac{2}{3}\right)^2+x^2}$
$=\frac{1}{9} \times \frac{1}{\frac{2}{3}}\left[\tan ^{-1} \frac{x}{\frac{2}{3}}\right]_0^{\frac{2}{3}}$
$=\frac{1}{6} \times \frac{\pi}{4}=\frac{\pi}{24}$

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